The present invention relates to a commutator provided with a short-circuit member for short-circuiting a plurality of segments to be set to the same electric potential. Further, the present invention relates to a direct-current motor provided with the commutator, and further relates to a manufacturing method of the commutator.
A plurality of segments are arranged on an outer circumferential surface of a columnar commutator. In general, the number of the segments is set to a least common multiple of the number of magnetic poles (that is, the number of field poles) of magnets in a stator of a direct-current motor, and the number of teeth (that is, the number of salient magnetic poles) in an armature core. Japanese Laid-Open Patent Publication No. 2005-137193 discloses a plate-like short-circuit member for short-circuiting predetermined segments with each other.
FIG. 13 of the publication mentioned above discloses a first short-circuit member, and FIG. 17 of the publication mentioned above discloses a second short-circuit member. An end in an axial direction of each of the segments has a locking recess, and the first short-circuit member has the same number of locking projections as the segments. Each of the locking projections is inserted to the corresponding locking recess, and an arm defining the locking recess is swaged, so that the first short-circuit member is assembled in the segment.
The second short-circuit member has the same number of second locking projections as the segments. Each of the second locking projections protrudes radially outward. Each of the segments has a connection terminal protruding in an axial direction. The connection terminal is locked to the second locking projection in a circumferential direction, and is thereafter welded.
In order to downsize the dimension in the axial direction of the commutator, the short-circuit member is formed by a pressed product of a thin metal plate. Accordingly, the dimensional accuracy of the first-short-circuit member and the segments is not high, and if the positions of the locking projection and the locking recess are deviated, there is a risk that the short-circuit member is deformed in the case of engaging the first short-circuit member with the segment.
Further, if the second short-circuit member is simply arranged in the segment, the second short-circuit member tends to be circumferentially deviated from the segments. Accordingly, the assembly of the second short-circuit member with the segments is difficult.